A genetic approach was used to investigate whether the emergence of circadian rhythms in murine pups is dependent on a functional maternal clock. Arrhythmic females bearing either the mPer1^Brdm1/Per2^Brdm1 or mPer2^Brdm1/Cry1^-/- double-mutant genotype were crossed with wild-type males under constant darkness. The heterozygous offspring have the genetic constitution for a functional circadian clock. Individual pups born to arrhythmic mPer1^Brdm1/Per2^Brdm1 and mPer2^Brdm1/Cry1^-/- mothers in constant darkness without external zeitgeber developed normal circadian rhythms, but their clocks were less synchronized to each other compared to wild-type animals. These findings indicate that development of circadian rhythms does not depend on a functional circadian clock in maternal tissue, extending previous findings obtained from pups born to SCN-lesioned mothers.